Deashing of residual fractions



Feb. 23, 1960 c. N. KIMBERLIN, JR., Erm. 2,926,129

DEASHING oF RESIDUAL FRACTIoNs Filed June 13, 1958 DEASG or anemonaaimerions' Charles Newton Kimberiin, dr., and Clark Edward Adams, BatonRouge, La., and Wiiired 0. Tati, Westiield, NJ., assignors to EssoResearch and Engineering Company, a corporation of Delaware Application.lune 13, 1958, Serial No. 74L3'53 TCEairns. (Cl. Zeit- 86) The present`invention relates to the removal of metal- `lic contaminants frompetroleum oils and more particu- 'in which such petroleum fractions areburned as fuels. "in operations such as catalytic crocking,-hydroliningand the like, :the presence of very small concentrations 'of thesecontaminants in thefeed stream leads to the rapid poisoning `of thecatalyst, causing va `significant decrease in the product yield, anincrease in coke and gas production, and a marked shortening in the lifeof the catalyst. ln residual -type fuels, such contaminants attacktherefractories used to line boilers and combustion chambers; causeslagging and the'build-up of deposits upon boiler tubes, combustionchamber walls and the blades of gas turbines; and severely corrodehightemperature metallic surfaces with which they. come intoicontact.

Although there have been'numerous methods proposed in the past forremovingthese contaminants from high boiling petroleum fractions, it hasbeen found that such methods are largely ineffective, generally resultin the -loss of substantial quantities of theoil, and in most cases areprohibitively expensive. As a.result,'it hasgenerally been `necessary torestrict `the feed streamsto catalytic `petroleum processing units tothose fractions which boil 'below the-range in which the contaminantsare'found and to avoid as much as possiblethe use in fuels of fractionswhich'containthe contaminants in high concentrations.

The present invention provides a new and improved .process fortheremoval of iron, nickel, vanadium, and

other metallic contaminants of the porphyrin type from fhigh lboilingpetroleum oils, and in .particular Vresidual oils. In accordance withthe present invention, such contaminants .are Vremo-ved by subjectingthe contaminated oil sequentially to a thermal treatment, treating theheat soakedrmaterial with l to l volumes of a lighthydrocarbonpreferably in the presence of an acidic gas. In a preferredembodiment of the invention the solventresidual oil mixture is alsosubjected to a sludging treatment with an immiscible sludging component`having a high affinity for aromatics, preferably anhydrous liquid Theconcentration of metallic contaminants and the ratio of volatile tonon-volatile contaminants in crude oils vary considerably. The metalscontent of any distillate fraction will therefore depend upon the typeand concentration of contaminants in the crudeoil from which thefraction was distilled, the boiling rangeof the fraction, and the amountof entrainment which-took place during the distillation. Heavygas oildistilled'from typical crudesmay contain from about'l to about 20 poundsfeedstock, and the like.

,HCL or BFS, preferably dry hydrogen chloride.

anhydrous .sulfur dioxide.

2,920,129 Patented Feb. 23, i960 HCE of metallic contaminants per 1000barrels. Residual fracA tions and gas oils derived from crudes which areparticu larly high in contaminants may contain as much as 300 pounds ofmetal per 1000 barrels. Similarly, in some fractions these contaminantsmay be predominantly of the volatile type and in others they may beessentially of the non-volatile type, depending upon the crude sourceand the conditions under which the fraction was obtained.

The heat soaking step of the present invention is carried out preferablyunder conditions of incipient cracking so that no signiiicant amount oflighter components are formed. The conditions required will depend upona combination of time and temperature, the nature of the The temperatureof thermal treatment, however, is below l000 F, and preferably belowabout 900 F. On the other hand, temperatures above Vabout 600 F. areneeded for sufficient reaction rate to maintain times within reasonablelimits. Pres- `sures may also be applied to the thermal treating step tomaintain the material in a substantially liquid phase.

The solvent precipitation step which follows is carried out in the heatsoaked feed stock directly. Preferred are light hydrocarbons boiling inthe range of about 55 to 400 F. As a result of the solvent addition,there is precipitated as a light, flocculent precipitate the so-calledasphaltene fraction, which is extremely diiiicult to remove from thelsolution phase. A portion of the porphyrins -are precipitated withthese asphaltenes, `while a portion remains in solution.

Accordingly, there is also employed as a metal coagulatingreagent anacidic material soluble in therpetroleum fractions, a hydrogen'halidesuch as anhydrous The treating temperature, the volume of hydrogenhalide employed and the pressure at which the treatment is carried out`may be varied considerably. It is preferred to treatthevsolvent-residual oil mixture at temperatures between about 70--and400 -F., although highertemperatures may be employed, and at Vpressuresranging from atmospheric to about `300 p.s.i.g., higher pressuresbeingalso permissible. The reaction time too may be varied from a rfewminutes to Ias much as a few hours, depending upon theV treatingconditions.

Though this combination'gives goed results in demetallizing residualoils, even better results can be obtained by addition of a sludgingcomponent, and in particular liquid A sludging action occurs whichservesto coagulate the llocculent asphaltene precipitate, enablingitsready separation as a sticky semifluid sludge. :The final .productVobtained by this combination processingis found to be extremely low inmetal .,content, thus enabling the residual oil to be 4used for turbinesandthe like.

The exact. nature and process of the present invention, its objects andadvantages, will be more fully understood from the following descriptionand drawing show- Aing schematically apreferred embodiment of theinvention.

Turning now to ,fthe drawing, reference numeral 1 `designates a crudeoil distillation zone which may constitute, for example, an atmosphericpipe still or a combination of atmospheric andl vacuum distillationtowers.

vCrude oil may be introduced into distillation zone l step.

Middle distillates may be withdrawn through line 5. These materials,kerosene and light gas oils, may boil4 up to 900 F. and aresubstantially metal free. A heavy gas oil fraction boiling in the rangeof between 950 F. and 1300 F. is withdrawn through line 6 and theresidual fraction, boiling above the heavy gas oil is taken oif asbottoms product through line 7. Both of these latter streams containsubstantial amounts of metallic constitu ents and may be subjectedseparately to the treating process of the present invention.

The thermal treating zone 8 to which the metal contaminated heavy oil ispassed via line 7, is preferably a closed, agitated vessel or drum. Thepressure during the heat soaking step is preferably maintained between200 to 1500 p.s.i.g. As indicated previously, it is advantageous tomaintain a temperature of from about 650 to 850 F. in this zione underconditions such that little if any cracking occurs. A residence periodof 0.1 to hours is desirable. The effect of the thermal treatment servesto increase markedly the susceptibility of the metallic constituents tolater coagulation by the acidic gas treatment, possibly by chang-ingeither the character of the porphyrin, the asphaltenes, or the oil.

The solvent precipitation step is carried out on the heat-soaked residuadirectly, and the latter is passed for this purpose through line 9 tocontacting tower 10. This may comprise one or more towers or othervessels adapted to permit the saturation of the oil with gaseous HCladmitted through line 15 under the desired conditions of temperature andpressure. Suitable coils, jacketing, or other Itemperature control meansare provided, as are means for agitation.

Solvent, which is preferably an aliphatic or naphthenic hydrocarbon ormixture having 5 to 10 carbon atoms, and which may advantageously be thenaphtha fraction withdrawn through line 4 from still 1, s introducedinto vessel 10 through line 12, in amounts of. from 0.1 to 10 volumesper volume of oil, preferably 0.3 to 3 volumes per volume of oil.Furthermore, in a preferred embodiment of the invention, 0.1 to 3volumes of liquid sulfur dioxide per volume of oil are admitted throughline 17 to effect sludging of the coagulated metallic components.

Reaction conditions within tower 10, which is preferably maintained asa-countercurrent reaction zone, are temperatures of 30 to 300 F. andpressures of 25 to 500 p.s.i.g. The residence time of the oil may rangefrom 5 to 100 minutes or more. The deashed oil-solvent mixture, alongwith gaseous HC1 or other acidic metal coagulating gas is passedoverhead via line 14 and passed through heater 16 to ash tower 18, wherethe hydrocarbon solvent along with HCl and any dissolved SO2 is lashed01T overhead through line 20, while oil of exceptionally low metalcontent is recovered from flash zone 18 through line 19. The iiashedsolvent and gases are passed to cooler 24 via lines 20 and 22, andthence to settler 26, which is maintained under conditions of decreasedtemperature and increased pressure to liquefy the SO2 Returning now totower 10, the semi-duid sludge is withdrawn downwardly through line 34and is, in a preferred embodiment of the present invention, furtherprocessed to recover the sulfur dioxide. This may be done by passing itthrough heating zone 36 into a fluidized solids ash zone 3S. Here `a bedof finely divided solids, preferably derived from previously treatedasphaltene, is maintained `as a dense, uidized bed of solids maintainedby an upward owing gas stream admitted through line 41. This bed ofsolids may be at a temperature of about 100 to l000 F., and the sludgeis deposited thereon,l whereby it is decomposed to a solid carbonaceousmaterial and gaseous SO2 and hydrocarbon. These gases are Withdrawnthrough cyclone 40 equipped with dipleg 42 for return of fines to theuidized bed, and are passed via lines 43 and 22 to settler 26. A portionis recycled via line 41 to reactor 38 to maintain the bed in uidizedcondition. Solid carbonaceous residue may be withdrawn through line 4Sand he used as solid fuel.

In the settling zone, which is adapted to settle out and separate liquidSO2 from solvent hydrocarbon, HC1 may be withdrawn overhead asuncondensed gas via line 28 for recycle to the system or may be recycleddissolved in liquid streams. Similarly, the hydrocarbon solvent forms anupper layer and is passed, in whole or in part, via line 32 to tower 10.Sulfur dioxide `is likewise recycled vifa line 30 to tower 10.

The process of the present invention may be subjected to many variationswithout departing from its spirit. Thus, instead of separately heattreating the oil prior to addition of solvent, it may be desirable,under certain circumstances, to thermally treat the oil-solvent mixturepreferably after saturation with the coagulating gas. IIn still anothermodification, total crude, from which fixed gases have been stripped,may be fed to the heat soaking vessel 8 and then to the countercurrentcontacting tower l10. Naphtha recycle is fed to the top of the towerequivalent to about 0.1 to l0 volumes on feed. The naphtha cut may be ofvarious boiling ranges or the total fraction boiling up to about 400 F.The naphtha-deashed oil solution is taken overhead from the contactingtower to a distillation tower where the naphtha recycle stream is cutout and excess naphtha from the crude taken oi as make naphtha. TheSO2-residue stream is taken from the bottom of the tower and decomposedas described hitherto. The SO2- HC1 fraction is taken overhead from thestill and compressed for recycling. Operating in this manner integratesthe distillation step after the solvent precipitation process, andproduces both the precipitant for the demetallizing process as well asany other cut desired in the "crude distillation step.

The process of the present invention yields an oil with very, low metalcontent from a highly contaminated stream, as shown below.

The following experiments were carried out with Bachaquero crude toppedat 400 F. in order to illustrate the effects of the variables involved.The Bachaquero topped crude is representative of the Venezuelan heavylake crudes containing large amounts of vanadium and nickel components.The sample used had a gravity of 14.1 API, a Furol viscosity of 187 SSFat 122 F., and contained 450 p.p.m. vanadium, 50 p.p.m. nickel, 2.3 wt.percent sulfur and 0.38 wt. percent nitrogen with a Connadson carboncontent of 11.3 Wt. percent.

The data below show the superior selectivity obtained by treatment withheavier hydrocarbons as compared with conventional deasphalting usingpropane. The propane deasphalting results are taken from correlations toshow data at both the same yield and at the same degree of metalsremoval. Results were obtained with the Bachaquero topped crude whichhad not been subjected to heat treatment.

Recovered Oil Treatment Vol. P.p.m. Percent Ni-l-V Yield 3 Vol.Pantano/1 Vol. Feed 94. 4 137 Propane Deasphalting:

Same Yield 94. 4 340 Same Metals Removal 79. 4 137 3Vol. Hexane/l V01.Feed 97.0 122 erogare@ content. These treatments were lcarriedout withBah` aquero topped crude after the indicated heat treatment by adding 3volumes of nepentane, saturatingthe mixture with anhydrous HC1 Igas andadding about one-half volume of liquid sulfur dioxide. Under theseconditions the precipitate immediately separated as a semi-iluid sludgeat the bottom of the reaction vessel.

Heat treatment for shorter periods of time at higher temperatures doesnot appear as lgood for metals removal as longer heating at lowtemperatures.

Data obtained with Bachaquero topped crude heat soaked for 4 hours at725 F. show the effect of the vari- The combination of both treatmentwith HC1 gas and sludging with liquid sulfur dioxide gives much bettermetals removal than either treatment alone. The above data also showthat a CS/Cq light naphtha boiling from about 110 to 180 F. is asatisfactory diluent. This material gives somewhat poorer metals removalthan the light n-paraflins because of the enhanced solvent power of thebenzene contained therein. The ready availability of such naphthafractions, however, oisets this slight disadvantage. Data obtained withthe naphtha also show that the degree of metals removal can becontrolled by the amount of diluent added, larger amounts removing moremetals, although equivolume naphtha is still very eifective.

The following data show that in addition to metals removal there areother quality improvements for the oil product such as increasedgravity, decreased Conradson carbon, decreased viscosity and decreasednitrogen content. All of these improvements increase the value of thefeed for catalytic cracking and other general uses.

Severe solvent precipitation treatment gives product approachingcatalytic cracking feed quality Product- 3/1 Pentane-l-HCl--Soz Baeha-Sludging Feed Heat Treatment quero Topped Crude 4 His. 4 Hrs. 4 Hrs.

N one 700 725 75 Vol. Percent Oil 100 89 86 85 89 Oil Inspections:

Gravity, API 14.1 19.8 21. 3 23.1 27. 3 Con, C., Wt. Percent.-. 11.3 4 03.1 2.5 1.4 P.p.m. Nickel 50 5 2 l. 5 1. 5 P.p.rn. Vanadium 450 84 10 2.5 2 Wt. Percent Sulfun 2 3 2. 2 1. 7 1. 8 1.7 Wt. Percent Nitrrgen... 058 0 23 0.14 0.07 0.04 Viso., SSF 122 F. 187 37 20 12 i6 Theffollowing'data .showthat the 700.F.l bottoms of -Bahaquero cmde'representing-thebottom 76% of the topped crudeis similarly improved by this treatment.Also data vare included which show that a domestic crude, 400 'F.Hawkinstopped crude,of much lower metals vcontent isimproved `by thistreatment. lThese feeds i were heatsoaked for 4 hours at 700 F. beforebeing treated with 3 volumes of n-pentane, saturated with HC1 andsludged ,with 0.5 'volume of liquid sulfur dioxide.

' Wt. SSF Vol. P.p.rn. API Percent 122 Percent Ni-I-V Gravity Cn., F.

700 F.|Bachaquero:

Feed 580 9. 8 14. 8 5, 300 80.5 23 19.0 4.0 42

In an -additional experiment a mixture of Bachaquelro topped crude andthree volumes of n-pen-tane saturated with HC1 gas was heat-soaked for 4hours at 700 F. The product oil was recovered in 89 vol. percent yieldon feed land had a nickel plus vanadium content of 20 ppm. These resultsare similar to those expected for treatment of the feed heat-soakedunder the same condi tions with 3 volumes of n-pentane and saturatedwith HCl gas.

What is claimed is:

1. An improved process for upgrading a metallic contarninated petroleumfraction including constituents boiling above about 950 F. whichcomprises subjecting said fraction to an initial thermal treatment at atemperature between about 600 to 900 F. for a period of 0.1 to 5 hours,thereafter contacting said fraction in a precipitation zone with 0.1 tol0 volumes of a light hydrocarbon per volume of oil, an acid gas andabout 0.1 to 3.0 volumes of liquid SO2 per volume of oil, therebyprecipitating and coagulating metallic contaminants and separating aheavy oil substantially free from the precipitated and coagulatedmetallic contaminants.

2. The process of claim 1 wherein said acid gas is hydrogen chloride.

3. An improved process for upgrading a metal contaminated petroleumfraction containing constituents boiling above 950 P. which comprisesheat-soaking said fraction at a temperature of from about 650 to 850 F.for a period of about 0.1 to about 5 hours, in a heat soaking zone,thereafter mixing said heat soaked oil with 0.1 to l0 volumes of ahydrocarbon having from 5 to 10 carbon atoms in a precipitation zone,saturating said mixture with 4gaseous HC1, maintaining precipitationconditions of 30 to 300 F. and 25 to 500 p.s.i.g. in said Zone, sludgingsaid mixture with 0.1 to 3 volumes per volume oil of liquid anhydrousSO2, and recovering a heavy oil greatly depleted in metallic impurities.

4. The process of claim 3 wherein said oil is heat soaked for about 4hours at abou-t 750 F.

5. The process of claim 3 wherein topped crude is passed sequentially tosaid heat soaking zone and said precipitation zone, a naphtha fractionpassed to said zone, a mixture of naphtha and deashed oil withdrawn fromthe upper portion of said zone and passed to a distillation zone.

6. The process of claim 3 wherein a sludge formed in said processrisdecomposed into solid carbouaceous material and gaseous SO2 andhydrocarbons by directly contacting said sludge in a coking zone with abed of iluidized solid carbonaceous material heated to a temperature inthe range of about 100 F. to about 1000 F. and maintaining said bed in alluidized state by recycling a portion of the gaseous S02 andhydrocarbon liberated in said ooking zone.

7. The process of claim 6 wherein said heavy oil is recovered by passinga liquid mixture separated from the sludge to a ashing zone, withdrawingfrom said ashing zone a gaseous mixture of said hydrocarbon, HC1 andSO2, combining said gaseous mixture with a portion of the gaseswithdrawn from the coking zone, passing said gases to a settling zonemaintained at conditions of decreased temperature and increased pressureto condense the gaseous SO2 and hydrocarbon while maintaining the HC1 ina gaseous state and separately withdrawing from said settling zone aliquid SO2 stream, a liquid hydrocarbon solvent stream and a gaseous HC1stream and recycling said streams to the precipitation zone.

References Cited in the le of this patent UNITED STATES PATENTS2,130,147 Milmore Sept. 13, 1938 2,188,012 Pilat et al. Ian. 23, 19402,650,898 Case Sept. 1, 1953 2,685,561 Whiteley et a1. Aug. 3, 19542,727,853 Hennig Dec. 20, 1955 2,780,587 Watkins Feb. 5, 1957 2,834,715Pratt May 13, 1958

1. AN IMPROVED PROCESS FOR UPGRADING A METALLIC CONTAMINATED PETROLEUMFRACTION INCLUDING CONSTITUENTS BOILING ABOVE ABOUT 950*F. WHICHCOMPRISES SUBJECTING SAID FRACTION TO AN INITIAL THERMAL TREATMENT AT ATEMPERATURE BETWEEN ABOUT 600* TO 900*F. FOR A PERIOD OF 0.1 5 HOURS,THEREAFTER CONTACTING SAID FRACTION IN A PRECIPITATION ZONE WITH 0.1 TO10 VALUMES OF A LIGHT HYDROCARBON PER VOLUME OF OIL, AN ACID GAS ANDABOUT 0.1 TO 3.0 VOLUMES OF LIQUID SO2 PER VOLUME OF OIL, THEREBYPERCIPITATING AND COAGULATING METALLIC CONTAMINANTS AND SEPARATING AHEAVY OIL SUBSTANTIALLY FREE FROM THE PRECIPITATED AND COAGULATEDMETALLIC CONTAMINANTS.